JP3981622B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering apparatus provided with a flow rate control valve for controlling a flow rate guided to a power cylinder side.
[0002]
[Prior art]
As a conventional flow control device, for example, a device described in Patent Document 1 is known. This conventional example is shown in FIG.
As shown, a pump P is connected to the flow control valve V.
The spool 1 of the flow rate control valve V has one end facing one pilot chamber 2 and the other end facing the other pilot chamber 3. The one pilot chamber 2 is always in communication with the pump P through the pump port 4. A spring 5 is interposed in the other pilot chamber 3. The pilot chambers 2 and 3 thus configured communicate with each other via a variable orifice a that controls the opening degree according to the excitation current I of the solenoid SOL.
[0003]
That is, one pilot chamber 2 communicates with the inflow side of the steering valve 9 that controls the power cylinder 8 via the flow path 6 → the variable orifice a → the flow path 7. The other pilot chamber 3 communicates with the inflow side of the steering valve 9 via the flow path 10 and the flow path 7.
Therefore, both the pilot chambers 2 and 3 communicate with each other through the variable orifice a, and the pressure on the upstream side of the variable orifice a acts on one pilot chamber 2 and the pressure on the downstream side is in the other pilot chamber. 3 will be affected.
[0004]
The spool 1 maintains a position where the acting force of one pilot chamber 2 and the acting force of the other pilot chamber 3 and the acting force of the spring 5 are balanced. In the balanced position, the spool port 11 is opened. The degree is decided.
Now, if the pump drive source 12 which consists of an engine etc. has stopped, pressure oil will not be supplied to the pump port 4. FIG. If no pressure oil is supplied to the pump port 4, no pressure is generated in the pilot chambers 2 and 3, so that the spool 1 maintains the illustrated normal position by the action of the spring 5.
[0005]
When the pump P is driven from the above state and pressure oil is supplied to the pump port 4, a flow can be made to the variable orifice a, and a differential pressure is generated there. Due to this differential pressure, a pressure difference is generated between the pilot chambers 2 and 3, and the spool 1 moves against the spring 5 in accordance with the pressure difference and maintains the balance position.
As the spool 1 moves against the spring 5 in this way, the opening degree of the tank port 11 is increased, but the control flow rate guided to the steering valve 9 side according to the opening degree of the tank port 11 at this time A distribution ratio between QP and the return flow rate QT returned to the tank T or the pump P is determined. In other words, the control flow rate QP is determined according to the opening degree of the tank port 11.
[0006]
The fact that the control flow rate QP is controlled according to the opening degree of the tank port 11 determined by the moving position of the spool 1 as described above means that the control flow rate QP is finally determined according to the opening degree of the variable orifice a. become. This is because the movement position of the spool 1 is determined by the pressure difference between the pilot chambers 2 and 3, and the opening of the variable orifice a determines this pressure difference.
[0007]
Therefore, in order to control the control flow rate QP according to the vehicle speed and the steering situation, it is only necessary to control the opening of the variable orifice a, that is, the excitation current of the solenoid SOL.
This is because the opening of the variable orifice a can be arbitrarily controlled from the maximum to the minimum depending on the magnitude of the excitation current of the solenoid SOL.
[0008]
The steering valve 9 controls the pressure of the power cylinder 8 in accordance with an input torque (steering torque) of a steering wheel (not shown). For example, if the steering torque is large, the supply amount to the power cylinder 8 is increased, and if the steering torque is small, the pressure of the power cylinder 8 is decreased accordingly. The switching amount of the steering torque and the steering valve 9 is determined by a torsional reaction force such as a torsion bar (not shown).
[0009]
If the switching amount of the steering valve 9 is increased when the steering torque is large as described above, the assist force by the power cylinder 8 is increased accordingly. On the contrary, if the switching amount of the steering valve 9 is reduced, the assist force is reduced.
If the necessary (required) flow rate QM of the power cylinder 8 determined by the moving speed of the piston and the control flow rate QP determined by the flow rate control valve V are made as equal as possible, the energy loss on the pump P side can be kept low. This is because the energy loss on the pump P side is caused by the difference between the control flow rate QP and the required flow rate QM of the power cylinder 8.
[0010]
In order to make the control flow rate QP as close as possible to the required flow rate QM of the power cylinder 8 as described above, it is the solenoid current command value SI for the solenoid SOL that controls the opening of the variable orifice a. The controller C controls the SI.
A steering angle sensor 16 and a vehicle speed sensor 17 are connected to the controller C, and the excitation current of the solenoid SOL is controlled based on the output signals of both sensors.
[0011]
In the figure, reference numeral 18 denotes a slit formed at the tip of the spool 1, and one pilot chamber 2 is always in communication with the flow path 7 through the slit 18 even when the spool 1 is at the position shown in the figure. ing. In other words, even when the spool 1 is in the illustrated state and the flow path 6 is closed, the oil discharged from the pump P is supplied to the steering valve 9 side through the slit 18. ing.
[0012]
Although the flow rate is very small as described above, the pressure oil is supplied to the steering valve 9 because the purpose is to prevent disturbance such as kickback and to ensure responsiveness.
Reference numeral 19 denotes a drive device for the solenoid SOL connected between the controller C and the solenoid SOL.
Reference numerals 13 and 14 are throttles, and reference numeral 15 is a relief valve.
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-260917 (pages 3 to 6, FIG. 1)
[0014]
[Problems to be solved by the invention]
In the conventional apparatus as described above, a steering angle sensor is connected to the controller C, and the excitation current of the solenoid SOL is controlled based on the output signal of this sensor. That is, if the steering angle signal from the steering angle sensor is increased, the basic solenoid current command value Ib output from the controller C is also increased. If the basic solenoid current command value Ib is large, the opening of the variable orifice a is kept large and the supply flow rate to the power cylinder increases.
However, for example, in an interchange on an expressway, the vehicle may turn while maintaining a constant steering angle. In this case, the steering angle is increased to some extent, but the steering wheel is kept constant. In other words, the steering wheel is in the steering holding state. Regardless of the steering wheel being held, the flow rate corresponding to the steering angle is supplied to the power cylinder, and the assist force is exhibited.
[0015]
Actually, the assisting force corresponding to the steering angle is exhibited even in the state where the steering is maintained, so that the steering force of the steering wheel is too light.
Moreover, since the assist force more than necessary is exhibited as described above, there is a problem that energy loss is generated accordingly.
[0016]
An object of the present invention is to provide a power steering device capable of preventing the steering wheel from becoming extremely light and realizing energy saving even in a steered state where the steering wheel is kept constant. It is.
[0017]
[Means for Solving the Problems]
A first invention includes a steering valve that controls a power cylinder, a variable orifice provided upstream of the steering valve, a solenoid that controls the opening of the variable orifice, a controller that controls the solenoid exciting current, A flow rate control valve that distributes a flow rate supplied from the pump to a control flow rate that leads to the steering valve according to the opening of the variable orifice and a return flow rate that is circulated to the tank or the pump, a steering angle sensor that detects a steering angle, A turning detection means for detecting a turning state of the vehicle , and the controller outputs a solenoid current command value as a basis of a solenoid excitation current based on the steering angle, and at the time of turning by a signal from the turning detection means. If it is determined that there is, then the solenoid current command value is multiplied by a constant α <1, Characterized by relatively small degree of opening of the variable orifice.
[0018]
The second invention comprises steering angular velocity specifying means for detecting or calculating the steering angular velocity, and the controller determines a solenoid current command value Iθ from the steering angular signal θ from the steering angle sensor, and the steering angular velocity signal from the steering angular velocity specifying means. A solenoid current command value Iω is determined from ω, and the solenoid current command value Iθ is multiplied by a constant α <1, and the multiplication result is added to the solenoid command value Iω to obtain a basic solenoid current command value Ib. And
According to a third aspect of the present invention, the turning detection means comprises a lateral acceleration sensor that detects acceleration generated in the width direction of the vehicle, and the controller turns when the lateral acceleration signal g from the lateral acceleration sensor is greater than or equal to a reference value. It is determined that it is time, and the solenoid current command value is multiplied by a constant α <1 to relatively reduce the opening of the variable orifice.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention shown in FIG. 1 is characterized in that the turning state is determined by the controller C, and the opening of the variable orifice a is reduced in the turning state. This is the same as the conventional example shown in FIG.
Hereinafter, the controller C will be described in detail, and the same constituent elements as those in the related art will be denoted by the same reference numerals and description thereof will be omitted.
[0020]
The controller C is provided with a turning determination means 20, and a lateral acceleration signal g from a lateral acceleration sensor (not shown) is input to the turning determination means 20. The lateral acceleration sensor detects acceleration generated in the width direction of the vehicle, and this lateral acceleration sensor is the turning detection means in the present invention.
Further, the controller C is inputted with a steering angle signal θ, a steering angular velocity signal ω, and a vehicle speed signal v.
[0021]
The steering angle signal θ is calculated based on the steering angle detected by the steering angle sensor 16, and the solenoid current command value Iθ is determined based on the steering angle signal θ. Therefore, the steering angle sensor 16 is used as the steering angular velocity specifying means in the present invention.
The solenoid current command value Iθ is determined on the basis of a theoretical value at which the relationship between the steering angle signal θ and the control flow rate QP becomes a linear characteristic. However, the solenoid current command value Iθ is set to zero if the steering angle signal θ does not exceed a certain set value. That is, when the steering wheel is neutral or in the vicinity thereof, the solenoid current command value Iθ is set to zero.
[0022]
When the solenoid current command value Iθ is determined as described above, a constant α is output from the turning determination means 20, and the constant α is multiplied by the solenoid current command value Iθ.
That is, the turning determination means 20 detects whether or not the lateral acceleration signal g is greater than or equal to a reference value, and determines that the vehicle is turning when it is greater than or equal to the reference value. If it is determined that the vehicle is turning, the solenoid current command value Iθ is multiplied by a constant α <1. Since the constant α at this time is set to a number smaller than 1, the solenoid current command value Iθ can be reduced by multiplying the constant α.
[0023]
On the other hand, when the acceleration signal g is smaller than the reference value, the turning determination unit 20 determines that the vehicle is not turning and multiplies the solenoid current command value Iθ by a constant α = 1. Therefore, the solenoid current command value Iθ remains as it is.
[0024]
When the solenoid current command value Iθ is multiplied by the constant α <1 or the constant α = 1 as described above, the solenoid current command value Iω determined based on the steering angular velocity signal ω is added to the multiplied value. The steering angular velocity signal ω is calculated by differentiating the steering angle signal θ. However, the steering angular velocity signal ω may be obtained directly by a steering angular velocity sensor provided separately. In this case, the steering angular velocity specifying means becomes a steering angular velocity sensor.
[0025]
Further, the solenoid current command value Iω is determined based on a theoretical value in which the steering angular velocity signal ω and the control flow rate QP are linear characteristics. If the steering angular velocity signal ω does not exceed a certain set value, zero is output. That is, when the steering wheel is neutral or in the vicinity thereof, the solenoid current command value Iω is set to zero.
[0026]
When the solenoid current command value Iθ is multiplied by the constant α and the solenoid current command value Iω is added to the solenoid current command value Iθ as described above, the solenoid current command value Iv based on the vehicle speed signal v is added to the added value (Iθ × α + Iω). Multiply.
The solenoid current command value Iv based on the vehicle speed signal v outputs 1 when the vehicle speed is in the low speed range and outputs zero when the vehicle speed is high. Further, in the medium speed range between the low speed range and the high speed range, a value after the decimal point from 1 to zero is output.
[0027]
Accordingly, if (Iθ × α + Iω) is multiplied by the solenoid current command value Iv based on the vehicle speed signal v, (Iθ × α + Iω) is output as it is in the low speed region, and (Iθ × α + Iω) becomes zero in the high speed region. .
In the middle speed range, a value that is inversely proportional to the speed increases as the speed increases.
[0028]
Further, when (Iθ × α + Iω) × Iv is determined, the standby solenoid current command value Is is added to this value. This is output from the controller C as a basic solenoid current command value Ib, and the solenoid excitation current is controlled based on this basic solenoid current command value Ib.
[0029]
The standby solenoid current command value Is is for always supplying a predetermined current to the solenoid SOL that controls the opening of the variable orifice a. That is, even when the solenoid current command value based on the steering angle signal θ, the steering angular velocity signal ω, and the vehicle speed signal v is all zero, the standby orifice current command value Is maintains the constant opening of the variable orifice a so that a predetermined standby The flow rate QS is always supplied to the steering valve 9 side.
[0030]
The reason for securing the constant standby flow rate QS in this way is as follows. That is, when a drag due to kickback or other disturbances or self-aligning torque acts on the tire, it acts on the rod of the power cylinder 8, but even in such a case, the standby flow rate QS should be secured. This is because the tire can be prevented from wobbling. Moreover, if the standby flow rate QS is secured, the response can be improved as much as the target control flow rate can be reached in a shorter time than when there is no standby flow rate QS.
Moreover, since the standby flow rate is always ensured in any case, it is possible to counter disturbance due to kickback or the like even during straight traveling in a low speed region, and it is possible to maintain good responsiveness during steering.
[0031]
In the embodiment as described above, the turning determination means 20 determines that the vehicle is turning when the lateral acceleration signal g exceeds the reference. Therefore, even if the vehicle is turning while maintaining a steering angle at a constant steering angle, for example, at an interchange, if the lateral acceleration signal g exceeds the reference, it is determined that the vehicle is turning. Can do.
When it is determined that the vehicle is turning, the solenoid current command value Iθ is multiplied by a constant α <1 so that the solenoid current command value Iθ is substantially reduced. Therefore, the basic solenoid current command value Ib is reduced accordingly, and the flow rate supplied to the power cylinder can be suppressed.
[0032]
When turning while keeping the steering, the flow rate supplied to the power cylinder can be suppressed, so that the steering wheel can be prevented from becoming too light. Moreover, since the flow volume supplied to the power cylinder at the time of the said holding | maintenance can be suppressed, energy saving can be implement | achieved by that much.
[0033]
In the above embodiment, the lateral acceleration sensor is provided as the turning detection means. However, a steering angular velocity sensor may be used, or a steering angle sensor may be used. When the steering angular velocity sensor is used, when the steering angle is a certain value or more and the steering angular velocity is zero, it is determined that the vehicle is turning while maintaining the steering.
By using the steering angular velocity sensor in this way, it is not necessary to provide a turning detection means for specifically detecting turning. Therefore, the cost can be reduced accordingly.
When the steering angle sensor is used, the steering angular velocity can be calculated from the steering angle. Thus, by calculating and obtaining the steering angular velocity from the steering angle, it is only necessary to use the steering angle sensor, and it is not necessary to use a steering angular velocity sensor. Therefore, the cost can be reduced accordingly. The control method using only this steering angle sensor is the same as that using the steering angular velocity sensor. When the steering angle is a certain value or more and the steering angular velocity is zero, Judging that he is turning while keeping the steering wheel.
[0034]
It is also conceivable to provide a yaw rate sensor as the turning detection means. When the yaw rate signal based on the yaw rate sensor is equal to or greater than a certain value, it is determined that the vehicle is turning.
In any case, as long as the turning can be determined, it can be used as the turning detection means.
[0035]
Furthermore, although the constant α is multiplied by the solenoid current command value Iθ in the above embodiment, the present invention is not limited to this. For example, an addition value of the solenoid current command value Iθ and the solenoid current command value Iω, or a multiplication value of this value and the solenoid current command value Iv may be multiplied by the constant α. Further, the basic solenoid current command value Ib may be multiplied by a constant α. In any case, when it is determined that the vehicle is turning, the solenoid current command value that is the basis of the solenoid current for controlling the variable orifice a may be smaller than that in the case where normal control is performed.
[0036]
However, if the constant α is multiplied by the solenoid current command value Iθ before the solenoid current command value Iω is added, the steering response is not affected and a good steering feeling can be obtained. it can. This is because the steering angular velocity ω is originally added to improve responsiveness. Nevertheless, if the solenoid current command value Iω is added and then multiplied by the constant α, the improved response may be reduced. Therefore, in order to prevent this responsiveness from decreasing, the constant α is multiplied before the solenoid current command value Iω is added.
[0037]
【The invention's effect】
According to the first and third inventions, when it is determined that the controller is turning by the signal from the turning detection means, the solenoid current command value is multiplied by a constant α <1, and the opening of the variable orifice is set. We decided to make it relatively small. Therefore, it is possible to suppress the supply flow rate to the power cylinder even when the vehicle is turning while fixing the steering wheel. Since the supply flow rate to the power cylinder can be suppressed, it is possible to prevent the steering wheel from being too light. In addition, energy saving can be realized as much as the supply flow rate is suppressed.
[0038]
In the second invention, the solenoid current command value Iθ determined from the steering angle signal is multiplied by a constant α <1, and the solenoid command value Iω is added to the multiplied value to obtain the basic solenoid current command value Ib. Therefore, it is possible to obtain a good steering feeling that does not affect the responsiveness.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a control system for normal control of a controller according to an embodiment.
FIG. 2 is a circuit diagram of a conventional example.
[Explanation of symbols]
8 Power cylinder 9 Steering valve 16 Steering angle sensor V Flow control valve P Pump a Variable orifice QP Control flow QT Return flow C Controller θ Steering angle signal Ib Basic solenoid current command value

Claims (3)

Steering valve for controlling the power cylinder, a variable orifice provided upstream of the steering valve, a solenoid for controlling the opening of the variable orifice, a controller for controlling the solenoid excitation current, and a flow rate supplied from the pump A flow control valve that distributes the control flow to the steering valve according to the opening of the variable orifice and the return flow to be recirculated to the tank or pump, a steering angle sensor that detects the steering angle, and a vehicle turning state are detected And a controller that outputs a solenoid current command value that is a basis for the solenoid excitation current based on the steering angle, and that determines that the vehicle is turning based on a signal from the turning detection means. Multiplies the solenoid current command value by a constant α <1 to obtain the variable orifice. Power steering apparatus characterized by the opening relatively small.   Steering angular velocity specifying means for detecting or calculating the steering angular velocity is provided, the controller determines a solenoid current command value Iθ from the steering angular signal θ from the steering angle sensor, and the solenoid current command value from the steering angular velocity signal ω from the steering angular velocity specifying means. 2. The solenoid current command value Iθ is determined by multiplying the solenoid current command value Iθ by a constant α <1, and the solenoid command value Iω is added to the multiplied value to obtain a basic solenoid current command value Ib. Power steering device. The turning detection means includes a lateral acceleration sensor that detects acceleration generated in the width direction of the vehicle, and the controller determines that the vehicle is turning when the lateral acceleration signal g from the lateral acceleration sensor is equal to or greater than a reference value. 3. The power steering device according to claim 1, wherein the solenoid current command value is multiplied by a constant α <1 to relatively reduce the opening of the variable orifice.

Images